DBMaker: handle NPE from mmap file enable on in-memory store
DBMaker: handle NPE from mmap file enable on in-memory store

jankotek/MapDB,ringoluo/mapdb,pettermahlen/mapdb,binarytemple/mapdb,olupas/MapDB,lamfire/mapdb,ffjiao/mapdb,sumit784/mapdb,SleimanJneidi/mapdb,mebigfatguy/mapdb,olupas/MapDB,cocosli/mapdb,jankotek/mapdb,codeaudit/mapdb,jankotek/mapdb,jankotek/MapDB,morfeo8marc/mapdb,mebigfatguy/mapdb,hangum/mapdb